111837: He is not sure whether his sleep was deep or not; is his wudoo' invalid?

I read the answer number 36889 and knew that deep sleep invalidates the wudu’. Sometimes I sleep in the train or in the car and I can’t be sure if my sleep was deep or not. In this case is my wudu’ considered invalid?.

Praise be to Allaah.

If a Muslim does wudoo’, this wudoo' cannot be ruled invalid
unless there is certainty that what invalidates wudoo' has occurred. Mere
uncertainty -- even if this uncertainty is strong – does not mean that
wudoo' is invalidated.

Al-Bukhaari (137) and Muslim (361) narrated that a complaint
was made to the Prophet (blessings and peace of Allah be upon him) about
when one thinks that something has happened whilst he praying. He said: “Do
not stop until you hear a sound or notice a smell.”

Al-Nawawi (may Allah have mercy on him) said in Sharh
Saheeh Muslim:

The words of the Prophet (blessings and peace of Allah be
upon him), “until you hear a sound or notice a smell” mean: until it is
known that one of them is present; hearing and smelling are not conditions
of wudoo’ being ruled invalid according to the consensus of the Muslims.

This hadeeth is one of the basic matters of Islam and an
important principle of fiqh, which is that things are ruled to remain as is
until there is certainty to the contrary, and mere doubt does not affect
them. An example of that is the issue in the chapter in which this hadeeth
is narrated, namely: If a person is certain that he is in a state of purity
and is uncertain as to whether it has been broken, then he is regarded as
still being in a state of purity, and it makes no difference whether this
uncertainty arises during the prayer or outside of prayer. This is our
opinion and the opinion of the majority of scholars, both earlier and
later.

Our companion said: There is no difference between a case
where his uncertainty is fifty-fifty and a case where he thinks that one or
the other is more likely. He does not have to do wudoo' in either case. End
quote.

If he is uncertain as to whether his sleep was deep or not,
then his wudoo’ is not invalidated thereby.

The kind of sleep in which a person is uncertain as to
whether he broke wind or not does not invalidate wudoo’, because purity is
established and certain, and cannot be removed by uncertainty. End quote.